Why do some molecules, like water, have positive and negative polar heads..?
Ionic bonding doesn’t apply with water, since water is a covalently-bonded compound. What happens is this: hydrogen and oxygen share electrons, but they don’t share evenly. That’s because oxygen is a lot more electronegative than hydrogen. It isn’t quite electronegative enough to completely remove hydrogen’s electron, but it’s close. So the covalent bond between hydrogen and oxygen is what we call a polar covalent bond. The bonding electrons are more strongly pulled to the oxygen end of the bond than to the hydrogen end. This leaves the hydrogen end with a partial positive charge because of its relative electron deficiency and causes a partial negative charge on the oxygen end. Now of course water has TWO oxygen-hydrogen bonds (since it has two hydrogen atoms), and you might expect that these polar bonds would cancel each other out. In fact this isn’t the case. The bonds are not oriented directly away from each other but instead are angled at about 104ยบ from each other. This means that
